<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../../jquery.min.js"></script>
    <style>
        * {
            margin: 0;
            padding: 0;
            list-style: none;
        }

        li {
            width: 50px;
            height: 30px;
            background-color: #ccc;
        }

        .father div {
            display: none;
            width: 100px;
            height: 100px;
            background-color: pink;
        }
    </style>
</head>

<body>
    <div class="father">
        <ul>
            <li>第一张</li>
            <li>第二张</li>
            <li>第三张</li>
            <li>第四张</li>
        </ul>
        <div>1</div>
        <div>2</div>
        <div>3</div>
        <div>4</div>
    </div>
    <script>
        $(function () {
            $("ul li").mouseover(function () {
                    $(this).siblings("li").css("background", "");
                    $(this).css("background", "red");
                    //当前小li的索引号
                    var index = $(this).index();
                    
                    $(".father div").eq(index).show();
                    $(".father div").eq(index).siblings("div").hide();
            })
        })
    </script>
</body>

</html>